Condensed Consolidating Financial Statements (Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Apr. 30, 2016	Apr. 30, 2015
Condensed Financial Statements, Captions [Line Items]
Net cash used in operating activities:	$ (475,675)	$ (378,246)
Sales, maturities of and payments received on AFS securities	58	32,103
Principal payments on mortgage loans held for investment, net	8,427	8,537
Capital expenditures	(6,246)	(8,689)
Payments made for business acquisitions, net of cash acquired	(1,635)	(12,271)
Loans made to franchisees	(2,219)	(2,582)
Repayments from franchisees	6,473	11,434
Other, net	220	3,562
Net cash provided by (used in) investing activities	5,078	32,094
Customer banking deposits, net	0	(268,532)
Dividends paid	(48,514)	(55,063)
Repurchase of common stock, including shares surrendered	(45,312)	(17,756)
Proceeds from exercise of stock options	1,639	13,015
Other, net	(24,779)	(22,413)
Net cash used in financing activities	(116,966)	(350,749)
Effects of exchange rates on cash	(2,367)	(10,907)
Net decrease in cash and cash equivalents	(589,930)	(707,808)
Cash & cash equivalents	306,871	1,299,382	$ 896,801	$ 2,007,190
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Dividends paid	(48,514)	(55,063)
Repurchase of common stock, including shares surrendered	(45,312)	(17,756)
Proceeds from exercise of stock options	1,639	13,015
Intercompany borrowings	92,187	59,804
Block Financial Issuer [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash used in operating activities:	(57,939)	27,342
Sales, maturities of and payments received on AFS securities	58	28,339
Principal payments on mortgage loans held for investment, net	8,427	8,537
Capital expenditures	(5)	(19)
Loans made to franchisees	(2,202)	(2,582)
Repayments from franchisees	6,305	11,288
Intercompany payments/investments in subsidiaries	40,217	2,226
Other, net	16	1,439
Net cash provided by (used in) investing activities	52,816	49,228
Customer banking deposits, net		(268,482)
Net cash used in financing activities		(268,482)
Net decrease in cash and cash equivalents	(5,123)	(191,912)
Cash & cash equivalents	3,902	286,165	9,025	478,077
Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash used in operating activities:	(417,736)	(405,588)
Sales, maturities of and payments received on AFS securities		3,764
Capital expenditures	(6,241)	(8,670)
Payments made for business acquisitions, net of cash acquired	(1,635)	(12,271)
Loans made to franchisees	(17)
Repayments from franchisees	168	146
Intercompany payments/investments in subsidiaries	(92,187)	(59,804)
Other, net	204	2,123
Net cash provided by (used in) investing activities	(99,708)	(74,712)
Intercompany borrowings	(40,217)	(2,226)
Other, net	(24,779)	(22,413)
Net cash used in financing activities	(64,996)	(24,639)
Effects of exchange rates on cash	(2,367)	(10,907)
Net decrease in cash and cash equivalents	(584,807)	(515,846)
Cash & cash equivalents	302,969	1,013,707	$ 887,776	1,529,553
Intersegment Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Intercompany payments/investments in subsidiaries	51,970	57,578
Net cash provided by (used in) investing activities	51,970	57,578
Customer banking deposits, net		(50)
Intercompany borrowings	(51,970)	(57,578)
Net cash used in financing activities	$ (51,970)	(57,628)
Net decrease in cash and cash equivalents		(50)
Cash & cash equivalents		$ (490)		$ (440)